Various methods are known for drying and sterilizing goods. Tumble dryers of a wide variety are able to dry fabrics at different temperatures. In such a case the constant movement of the goods is combined with the input of heated air. In addition to these tumble dryers there are also dryers in which the hanging goods are exposed to air which is either warmed or is at room temperature.
The sterilization of the laundry itself is not normally performed in the dryers, and additional procedures are necessary for this purpose. For example, various sterilization processes are known in the field of hygiene and microbiology; the methods relevant to the sterilization of laundry are discussed below.
Autoclaving at 121.degree. C. and 2 bar steam pressure is a widely used technique for disinfecting temperature-sensitive materials. This process is used primarily when the material cannot be expected to withstand temperatures of 160.degree. C. or more without damage.
Other means of sterilizing such heat-sensitive items, include exposing the goods to gases such as ethylene oxide, formaldehyde, chlorine, ozone, etc. The goods can also be disinfected in an aqueous medium with disinfectants containing, for example, oxidants or aldehyde groups (formaldehyde). Although these chemical processes can be effective. They are also very time-consuming.
Further, the sterilization of very delicate goods may be accomplished with irradiation with gamma rays; x-radiation cannot be used with a sufficient dosage rate to achieve sterilization.
With the modern-day method of laundering items at 30.degree., 60.degree. and 90.degree. C. it must basically be assumed that boiling the laundry is no longer practiced. Furthermore, many kinds of fabric are so delicate that washing at higher temperatures would be harmful to the materials. In all of today's washing methods, moreover, severe mechanical stresses are involved which also limit the level of the washing temperature. For the same reasons, tumble dryers for delicate goods cannot use temperatures higher than about 50.degree. to 60.degree. C., since otherwise the thermal and mechanical stresses would soon cause permanent damage.
From this it is apparent that, in today's washing processes followed by drying in tumble dryers, cleaning is quite possible, but subsequent sterilization of the laundry is not feasible. It must therefore be assumed that the dry laundry afterward is still infected with a load of germs.
Consequently, there is a need for subjecting laundered goods, articles of clothing, etc. to sterilization. Since fabrics are damaged at high temperatures such as 160.degree. C., the goods must be sterilized by autoclaving, by chemical substances, or by radiation.
Operating an autoclave requires technical skill and can be considerably dangerous to an untrained lay person. Both high temperatures, e.g., 121.degree. C., so that some parts of the apparatus are at that temperature, and a pressure of 2 bar must be built up, which calls for a pressure chamber which must have a complex opening system for equalizing the chamber and exterior pressures. An autoclave furthermore requires technical maintenance which considerably increases the cost of operating this system.
Articles of clothing are also sterilized by chemical methods such as those discussed above. It should be noted that some of the chemical substances involved can have negative effects on the skin of the wearer, because unless they are completely removed from the fabrics at the end of the sterilization process, substances of high molecular weight can remain in the goods and afterward produce defensive reactions in the wearers such as allergies, for example. Yet these chemical substances cause difficulties not just for the wearer but also in their removal. If gases are involved, they are often released into the atmosphere, and if liquids are involved they pollute the waste water which is released into the environment. Both contamination of the air and of the ground water must be avoided at all costs.
Even sterilization with gamma rays poses a certain problem: the germs are killed by this treatment without heating the goods or exposing them to chemicals, but it must be noted that such a dose of radiation cannot be achieved by an x-ray apparatus but only by natural radionucleotides. Consequently, the problem of installation costs is aggravated by the problem of disposal.
The invention is addressed to the problem of performing drying and sterilizing in a relatively simple manner, while at the same time minimizing the drying and sterilization time, keeping the costs reasonable, avoiding environmentally harmful gaseous or water-soluble substances, rendering the operation safe, simple and easy for technically untrained users, and moving the air with which the goods come in contact in the drying and sterilization processes within a closed circuit so that contamination of the environment will be impossible.